根据短文内容，从短文后的选项中选出能填入空白处的最佳选项，选项中有两项是多余的选项
It is well known that the increasing population problem is one of the greatest challenges in the world. ____  It has caused serious problems for many countries.
A report from the UN says the world’s population keeps on rising at a speed of about 78 million people every year. ____ In fact, population growth has slowed or even stopped in developed countries.
_________ On the one hand, it may lead to wars, hungers, illness and so on. On the other hand, the more people there are, the more natural resources we need. _____
At the beginning of the 21^st century, more than a billion people don’t have enough necessaries: medicine, water, houses and so on. ______

A．As a result, too many trees have been cut down and forests have disappeared in some places.

B．Luckily, people are trying to find ways to solve the problem.

C．Some countries encourage their people to have more babies.

D．Some scientists said that population growth would lead to many problems.

E. Most of the growth is taking place in developing countries.
F. The people in developed countries are cleverer.
G. The world’s population is growing faster and faster.